American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jan 1994
Vertical gradient of regional lung inflation in adult respiratory distress syndrome.
We obtained chest computed tomography (CT) sections in 12 normal subjects (controls) and 17 patients with the adult respiratory distress syndrome (ARDS) to investigate regional lung inflation. A basal CT section (just above the diaphragm) was obtained in the supine position at zero cm H2O end-expiratory pressure. In each CT section the distance from ventral to dorsal surface (hT) was divided into 10 equal intervals, and 10 lung levels from ventral (no. 1) to dorsal (no. 10) were defined. ⋯ The tissue volume, however, was 16.7 +/- 0.8 ml x m-2 in control subjects and 31.6 +/- 1.7 ml x m-2 in patients with ARDS (p < 0.01). The g/t ratio in level 1 averaged 4.7 +/- 0.5 in control subjects and 1.2 +/- 0.2 in patients with ARDS (p < 0.01), and this ratio decreased exponentially from level 1 to level 10, both in controls and patients with ARDS. The Kd constant of the exponential decrease was 13.9 +/- 1.3 cm in control subjects and 7.8 +/- 0.8 cm in patients with ARDS (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jan 1994
Editorial CommentViscosity versus composition in airway pathology.
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Am. J. Respir. Crit. Care Med. · Jan 1994
Aerosol deposition in mechanically ventilated patients. Optimizing nebulizer delivery.
Previous studies have suggested that nebulizers are inefficient in delivering aerosolized medication to the lung in patients supported by mechanical ventilation. In a recent bench study, we characterized factors that may affect aerosol delivery, i.e., nebulizer type, ventilator settings (duty cycle), volume fill, and humidification as well as technical factors affecting measurement of deposition (e.g., radiolabeled compounds). Utilizing the predictions from our bench data, the present study was designed to assess nebulized aerosol delivery to ventilated patients under optimal conditions. ⋯ Measured radioactivity at each site was expressed as a percentage of nebulizer charge (i.e., the quantity of radioactivity originally placed in the nebulizer). On average, 30.6 +/- 6.3% (SD) of the charge was inhaled by the ventilated patients. Mean deposition in the TT during inspiration was 2.6 +/- 0.5%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jan 1994
Comparative StudyAcoustic method to estimate the longitudinal area profile of endotracheal tubes.
A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. ⋯ Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.